Oh, no, Prince DEFINITELY "stroked" his guitar during the giant shadow sequence. Definitely. He's Prince, that's what he does. Everyone we were watching it with saw it, we rewound it watched again. No doubt about it. (I'm trying to find the moment on YouTube).
ETA: Found it. It's at about 4:28 into
this video that he strokes it. Then at about 4:39 he does a kinda suggestive thrust.